Reducing the modulation voltage error in MMCs by considering the capacitor voltage change within one PWM cycle for improved current control

The impact of capacitor voltage changes during the modulation period is examined in order to improve the arm voltage of a modular multilevel converter. Different methods are used to predict and compensate for the capacitor voltage change and the resulting arm voltage error, whereby two of the improvements provide a possibility to easily upgrade existing modulation algorithms. Simulation and measurement results demonstrate a reduced arm voltage error and thus a reduced circulating current in comparison to the case when the voltage change is neglected in the modulator.